The present invention relates to industrial fabrics, and to a method of manufacturing industrial fabrics.
The term “endless fabric” as used herein and in the following relates to a fabric which is closed during operation. The term “endless” should, in particular, be considered also to include the case where the fabric can be opened across the machine direction for mounting in an industrial process machine, and subsequently joined together by means of a locking seam.
The “fabric of yarn material” as used herein may in particular be some type of woven, knitted, arrays of MD or CD yarns or other nonwoven structures such as extruded meshes, and the term “fiber material” includes all types of batt layers and the like that can be used in an industrial process fabric.
Currently, some fabrics for industrial process applications, such as in the production of nonwovens by processes such as spin bonding or hydroentangling; or corrugator belts used in the production of corrugated boxboard, are manufactured mainly by a tubular weaving technique which is known to those skilled in the art and according to which the fabric is made in the form of a tube and the weft threads are alternately passing into an upper warp thread layer (upper cloth) and a lower warp thread layer (lower cloth). The extent of this “tube” in the transverse direction of the weaving loom thus corresponds to half the length of the final fabric. The width of the fabric is determined by the weaving length.
This known technique suffers from several shortcomings. For one, the length of a tubular-woven fabric is determined by the reed width in the weaving loom. A tubular-woven fabric thus has a given length which cannot be substantially modified afterwards and which therefore, during the very weaving operation, must be adjusted to precisely the machine in which the fabric is to be mounted. Hence, the fabric cannot be manufactured and kept in stock in large series, but must be manufactured to a specific order. This extends the delivery time and means low degree of utilization of the weaving equipment. Moreover, the weaving looms must be given a considerable width, preferably over 20 m to permit tubular weaving of all current lengths of fabric. The weaving looms therefore become both large and expensive.
Other fabrics are flat woven. That is, they are a flat woven, continuous band of material of warp (MD) and weft (CD) yarns. These bands are woven to a width that is approximately the width of the final end use fabric structure. The length required is formed by cutting from the band a length in excess of the required final fabric length. The two CD edges of the band are then prepared in one of the following manners: MD and CD yarns are interwoven from each end to join the fabric into a continuous loop or tube of the required length; warp yarns are woven back into the respective each end of the strip with a small loop formed. These loops on each end are then interdigitated and a pin or pintle is passed through them forming a seam. Or a set of metal clipper hooks can be embedded into each end of the fabric, the closed end of the “hook” having a protruding loop. Again these loops are interdigitated and a pin or pintle passed through them to connect the full width seam. Other methods can be used to join the two ends of the fabric together as known to those skilled in the art.
The need to weave the support structure to a width at least as great as the width required for the final fabric requires weaving looms greater than 160 inches (4 meters) up to approximately 560 inches (14 meters).
Seaming can also be an expensive and time consuming step. Also, the need for a seam often limits the weave pattern or number and size of the warp yarns in the body of the fabric below an optimum level for best fabric performance.
Furthermore, the design of many industrial process machines dictates that the fabrics/belts they use be seamable on the machine.
Accordingly, there is a current need to provide an efficient seamable industrial process fabric and a cost effective method for producing such a fabric.